The present invention relates to guide disks used to guide a lower end of a fuel injector needle during operation.
A number of prior art fuel injectors include a lower needle guide which guides a downstream end of a fuel injector needle during operation. The lower needle guide is located directly above the fuel injector valve seat and helps to maintain axial concentricity of the needle with respect to the valve seat. During manufacture of the fuel injector, the disk is fixedly connected to the valve seat, preferably by welding, crimping, or some other known technique.
In some cases, the lower guide is made from a thin disk in which a carefully dimensioned central opening has been formed, through which the injector needle reciprocates during operation, and in which an additional series of flow openings is formed radially around the central opening. The purpose of these openings is to allow fuel to flow through the lower guide without restricting that fuel flow.
However, dead spots where fuel does not flow tend to form in areas immediately downstream of the lower guide around the central opening and the flow openings. During hot fuel operations, after the fuel injector has been left soaking on a hot temperature engine, fuel in the injector downstream of the lower guide can start vaporizing, creating fuel bubbles which can be difficult to eliminate when the fuel system is restarted.
Additionally, the flow openings can force the fuel to flow around corners, which can induce unwanted turbulence which can add to bubble formation in that area.
It would be beneficial to provide a lower guide disk which does not trap fuel on a downstream side of the disk, thus eliminating vaporized fuel and reducing turbulence downstream of the disk.
Briefly, a fuel injector is provided. The fuel injector comprises a fuel metering member having first and second ends disposed along a longitudinal axis, a seat located within the fuel metering member proximate the second end, and a needle reciprocably disposed within the fuel metering member. The needle has a longitudinal needle axis. The fuel injector also comprises a guide disposed within the fuel metering member proximate to the seat. The guide includes a generally planar disk having a first surface, a second surface, and an outer perimeter. The guide also includes a generally concentric central opening extending therethrough. The central opening is sized to allow the reciprocating element to reciprocate therein. The guide also includes at least one inner opening extending between the first and second surfaces from the central opening toward the outer perimeter. The at least one inner opening extends generally parallel to the longitudinal axis.
Further, the present invention provides a fuel injector comprising a fuel metering member having first and second ends disposed along a longitudinal axis, a seat located within the fuel metering member proximate the second end, and a needle reciprocably disposed within the fuel metering member. The needle has a longitudinal needle axis. The fuel injector also comprises a guide disposed within the fuel metering member proximate to the seat. The guide includes a generally planar disk having a first surface, a second surface, and an outer perimeter being secured to the fuel metering member. The guide also includes a generally concentric central opening extending therethrough. The central opening guides the needle. The guide also includes at least one opening extending between the first and second surfaces. The at least one opening at the first surface is disposed at a first longitudinal distance from the seat opening, and the outer perimeter is disposed at a second longitudinal distance from the seat opening. The first distance is greater than the second distance.
A method of evacuating vapor bubbles proximate a valve seat in a fuel injector is also provided. The method comprises providing a fuel injector installed in an internal combustion engine. The fuel injector includes a fuel metering member having first and second ends disposed along a longitudinal axis, a seat located within the fuel metering member proximate the second end. The seat has a seat opening. The fuel injector also includes a needle reciprocably disposed within the fuel metering member. The needle has a longitudinal needle axis. The fuel injector also includes a guide disposed within the fuel metering member proximate to the seat. The guide includes a generally planar disk having a first surface, a second surface, and an outer perimeter being secured to the fuel metering member, a generally concentric central opening extending therethrough, the central opening guiding the needle, and at least one opening extending between the first and second surfaces. The at least one opening at the first surface is disposed at a first longitudinal distance from the seat opening. The outer perimeter is disposed at a second longitudinal distance from the seat opening. The first longitudinal distance is greater than the second longitudinal distance. The method further comprises operating the fuel injector; stopping the fuel injector; and allowing vapor bubbles formed between the guide and the seat to flow through the at least one opening.